X+X+X+Y+Y=20 X+Y+Y=14.6 x=?Y=?速度啊1分钟时间

二元函数f(x,y)=x+y/x-y,求f(y/x,x/y) [x(x-y)-y(x-y)+(x+y)(x-y)]÷2x其中x=2012 y=2013 先化简再求值(x-y)(x+y)-(x-2y) 的完全平方+x(3x-5y)-(x-y)(x-2y),其中x=1/2 y ) y=cos(x-y) x+y=5; x^y+y^x=17 因式分解下列式子：x(x-y)+y(y-x)=? y=[x-1], x+y/2+x-y/3=6,4(x+y)-3(x-y)=-20 {(x+y)/2+(x-y)/3=6 4(x+y)-3(x-y)=-20 4(x+y)-3(x-y)=-20,2/x+y+3/x-y=6 1.已知1/x+1/y=-1/x+y,则y/x+x/y=? {3(x+y)+3(y+x)=1,3(x+y)+4(y-x)=-1